Certain 2-amino-1,3,4-thiadiazoles

ABSTRACT

The preparation of 2-amino or substituted amino-5-substituted thiadiazoles are described. They are useful in the treatment of ascariasis and as intermediates for the preparation of, for example, 2-(2-amino-5-1,3,4-thiadiazolyl)-1-methyl-5nitroimidazole which has anti-protozoal and anti-bacterial properties.

United States Patent Remers et al.

CERTAIN 2-AMINO-l,3,4- THIADIAZOLES Inventors: William Alan Remers, Lafayette, lnd.; Gabriel Joseph Gibs, Pearl River, N.Y.; Martin Joseph Weiss, Oradell, NJ.

Assignee: American Cyanamid Company,

Stamford, Conn.

Filed: Oct. 30, 1970 Appl. No.: 85,736

Related US. Application Data Continuation-impart of Ser. No. 766,986, Oct. 11, 1968, Pat. No. 3,564,002.

US. Cl ..260/306.8 D, 424/270 Int. Cl. ..C07d 91/62 Field of Search ..260/306.8 D

[ Oct. 24, 1972 [56] References Cited UNITED STATES PATENTS 3,564,002 .2/1971 Remers et a! ..260/306.8 D

Primary Examiner-Alex Maze! Assistant Examiner-R. J. Gallagher Attorney-Emest Y. Miller 57] ABSTRACT 3 Claims, No Drawings CERTAIN Z-AMINO-l ,3.4-THIADIAZOLES This application is a continuation-in-part of our application Ser. No. 766,986, filed Oct. 11, 1968, now US. Pat. No. 3,564,002.

SUMMARY OF THE INVENTION The present invention relates to novel 2-amino or substituted amino-S-substituted 1,3,4-thiadiazoles and methods of preparing the same.

The compounds of this invention can be defined as those of the formulas when taken together is the cyano group. The term lower alkoxy is intended to include those alkoxy groups having one to four carbon atoms. The term lower alkanoyl includes those having one to four carbon atoms in addition to the carbonyl group.

The compounds of the present invention are usually crystalline solids somewhat soluble in water. Those capable of forming acid addition salts in the form of salts are more water soluble.

The compounds of the present invention are useful as intermediates for the preparation of compounds of Formula A, wherein R is lower alkyl, as well as of the N-acetyl derivatives thereof. H W

L WLW The compounds of Formula (A) and the corresponding N-acetyl derivatives show very important oral, broad-spectrum antibacterial activity as well as activity against colibacillosis, fowl typhoid, enteritis and trichomonas vaginalis infections.

The preparation of the compounds of the present invention and the conversion to the highly physiologically active 2-(2-amino-5-1,3,4-thiadiazolyl)-l-methyl- 5'nitmimidaml9 is shwn n t f l wiasflmvsl ss FLOWYSHEET \CH 015! HNNHC 221, I I T 2 g NH CHO]: 01 s I 1 11 III mmImNOH l l H NHr-LS o=N0H IV IAczO HCl. VII

WUG 1...

XII IHOH I I N NH XIII in which Ac is lower alkanoyl.

The initial 5-dichloromethyl-2-aminothiadiazole (III) is obtained by condensing dichloroacetic acid with thiosemicarbazide in the presence of phosphorus oxychloride. The latter reagent serves two functions; (1) to'convert in situ the haloacetic acid to the corresponding acid chloride, and (2) in the absence of a second molar equivalent of acid halide or anhydride to activate the intermediate N acyl thiosemicarbazide to cyclization via an intermediate such as B.

Hydrolysis of the dichloromethyl derivative (III) in the presence of hydroxylamine gives the amino aldoxime (IV) treatment of which with acetic anhydride furnishes the corresponding acetamido nitrile (V). The nitrile function is usefulfor the development of the imidazole ring, which is accomplished by conversion to the iminoether (VI) and subsequent treatment with aminoacetaldehyde acetal. The resulting amidine derivative (VII) is cyclized by treatment with strong Ptiqah y .$s!; uris s d, a d t aLI i a The activity of the latter compound and derivatives is shown hereinafter in the examples.

DETAILED DESCRIPTION The following examples describe in detail the preparation of representative compounds within the scope of the present invention and testing data on conversion products of the present compounds.

EXAMPLE 1 Preparation thiadiazole and 2-Amino-l,3,4-thiadiazole-2-carboxaldehyde Oxime' To an ice-cooled mixture of 9.11 g. (0.1 mole) of thi'osemicarbazide and 12.89 g. (0.1 mole) of dichloroacetic acid is added slowly, withvigorous stirring, 30.67 g. (18 ml. 0.2 mole) of phosphorus oxychloride. After this addition is complete the ice bath is replaced by a water bath and the temperature is raised gradually to 70C. Vigorous evolution of hydrogen chloride ensues as the temperature nears 70C. and the mixture is briefly cooled to control foaming. After ca. 70 min. gas evolution ceases. The resulting viscous solution is stirred at 70C. for an additional hour and then is cooled in an. ice bath. To the thus-formed 2- amino-5-dic'hloromethyl-l,3,4-thiadiazole, a solution of 30 g. of hydroxylamine hydrochloride in 50 ml. of water is added followed by 20 ml. of concentrated hydrochloric acid immediately afterward. The mixture is stirred at 70C. for 5 hours, cooled and filtered to remove some excess hydroxylamine hydrochloride. When the pH of the filtrate is adjusted to 6.0 by addition of 5N sodium hydroxide, 5-amino-l,3,4- thiadiazole-2-carboxaldehyde oxime crystallizes as brownish prisms. It is washed with cold water and dried under reduced pressure. A 10.8 g. yield of material suitable for direct conversion to the nitrile is obtained (if desired, the oxime may. be recrystallized from ethanol or from methanol-water).

EXAMPLE 2 Preparation of 2-Acetamido-1,3,4-thiadiazole-5-carbonitrile A mixture of 10.8 g. of the oxime (Example 1) and 100 ml. of acetic anhydride is heated at reflux temperature for 18 hours and then is concentrated under reduced pressure. The tan solid residue (13 g.) is dissolved in 50 ml. of hot methanol, diluted with 50 ml. of water and cooled. Yellow crystals of the nitrile are obtained. The yield of product melting at 226-230C. is 8.5 g.

EXAMPLE 3 Preparation of S-Acetamido-l,3,4-thiadiazole-2-carboximidic Acid Methyl Ester Hydrochloride A mixture of 8.40 g. (50 mmoles) of S-acetamidol,3,4-thiadiazole-2-carbonitrile (Example 2) and 80 ml. of tetrahydrofuran is treated with 4.05 ml. (3.20 g. 100 mmoles) of methanol, chilled in an ice bath and saturated with anhydrous hydrogen chloride. Asolid of I 2-Amino-5-dichloromethyl-l,3,4-

4 forms during this saturation process. The mixture is kept at 5C. for 22 hours and then filtered. The solid imino'ether hydrochloride is washed well with ether and can be used at this stage (melting point 202208 PC; A max. 2.9, 3.1, 3.4, 5.9g. directly in thenext Example l2.

EXAMPLE4 Preparation of 5-Acetamido-N-(2,2-diethoxyethy1)l,3,4-thiadiazole 2-carboxamidine Hydrochloride The imino ether hydrochloride from Example 3 is added to an ice-cooled mixture of 5.25 g. (50 moles) of aminoacetaldehyde diethylacetal and ml. of methanol. The resulting mixture is heated at reflux temperature for 19 hours and is then concentrated under reduced pressure. The gummy residue is triturated with ether containing a little methanol until the amidine hydrochloride crystallizes. The product is washed with ether and air dried. It has A max. 2.9, 3.4 (broad), 5.9 u; 278 mu.

EXAMPLE 5 Preparation of 2-Acetamido-5-(2-imidazo1yl)-l ,3 ,4- thiadiazole The amide of Example 4 is added in portions to 20 ml. of concentrated sulfuric acid. The mixture, which foams and becomes warm, is cooled in a water bath when necessary. When complete solution is obtained it is poured onto 100 g. of ice and the resulting solution (filtered if necessary) is brought to pH 6 with 5N sodium hydroxide (ice cooling). The precipitate that forms is washed with water and dried in air. This procedure gives 5.75 g. of yellow solid product that does not melt below 320C.

EXAMPLE 6 EXAMPLE 7 Preparation of 2-Amino-5-( 1-methy1-2-imidazolyl)- l ,3 ,4-thiadiazole A mixture of 307 mg. (1.85 mmoles) of 2-amino-5- (2-imidazolyl)-l,3,4-thiadiazole (Example 6) and 3.8 m1. of 0.5 N sodium hydroxide is stirred and filtered to .remove some insoluble material. The filtrate istreated Preparation of 2-Acetamido-5-( l-methyl-2- imidazolyl)- l ,3,4-thiadiazole and 2-Acetarnido-5-( lmethyl-S-nitro-Z-imidazolyl )-1 ,3 ,4-thiadiazole A mixture of 124 mg. (0.7 mole) of 2-amino-5-( lmethyl-2-imidazolyl)-l,3,4-thiadiazole (Example 7) and 0.4 ml. of acetic anhydride is heated on a steam bath for minutes to give 2-acetamido-5-( l-methyl-2- imidazolyl)-l ,3,4-thiadiazole. To the resulting mixture is added 1.2 ml. of acetic acid, 0.05 ml. of 70 percent nitric acid, and an additional 0.2 ml. of acetic anhydride. The mixture is heated on a steam bath and is treated with 0.02 ml. of 70 percent nitric acid. A vigorous reaction ensues and brown gas is evolved. in about 10 minutes a clear solution is obtained. It is concentrated and the residue is treated with water. The yellow solid that forms is washed with water and is dried in air. This procedure gives 61 mg. of 2- acetamido-5-( l-methyl-S -nitro-2-imidazolyl)-l ,3 ,4- thiadiazole.

EXAMPLE 9 Preparation of 2-Amino-5-( l-methyl-S-nitro-Z- imidazolyl )-l ,3 ,4-thiadiazole A mixture of 60 mg. of crude Z-acetamido-S-(lmethyl-5-nitro-2-imidazolyl)- l ,3 ,4-thiadiazole (Example 8) and 0.2 ml. of concentrated hydrochloric acid is heated on a steam bath for minutes, cooled, and concentrated under reduced pressure. The residue is treated with l N hydroxide until pH 7 is obtained, whereupon solid separates. This solid is washed with water and dried in air, yield 23 mg. Partition chromatography on diatomaceous earth with a heptane- Niacin 27.5 mg. Pantothenic Acid 8.8 mg. Chlorine Chloride 500 mg. Folic Acid 1.43 mg. Menadione Sodium Bisulfate 1.1 mg. Vitamin 8,, 11 mcg. Ground Yellow Corn, Fine to 5 gm.

EXAMPLE 11 The Use Of 2-(2-Am1no-5-1,3,4-tluadiazolyD-l- 0 methyl-S-nitro-imidazole And its Acetyl Derivative In Controlling Colibacillosis This example demonstrates the effectiveness of 2-(2- amino-S- 1 ,3,4-thiadiazolyl)- 1 -methyl-5-nitroimidazole (Example 9) in controlling colibacillosis in poultry.

ethyl acetate-methanol-water (70:30:1516) system gives several fractions absorbing at 357 my" The largest of these fractions, upon concentration, affords yellow crystals which are identical in infrared spectrum and behavior on thin-layer chromatography with authentic sample of 2-amino-5-(l-methyl-5-nitro-2-imidazolyl)- l ,3 ,4-thiadiazole.

EXAMPLE 10 Preparation of Chick Diet The following feed composition is employed in all the poultry experiments hereinafter set forth except where otherwise stated:

Vitamin Pre-Mix 0.5% Trace Minerals 0.1% Sodium Chloride 0.3% Dicalcium Phosphate 1.2% Ground Limestone 0.5% Stabilized Fat 4% Dehydrated Alfalfa, 17% 2% Corn Gluten Meal, 41% 5% Menhaden Fish Meal, 60% 5% Soybean Oil Meal, 44% 30% Ground Yellow Com, Fine To l00% The vitamin pre-mix in the above feed composition is prepared from the following formulation. The expressions of quantity relate to units per kilogram of the feed composition.

Butylated Hydroxy Toluene 125 mg. dl-Methione 500 mg. Vitamin A 3300 LU. Vitamin D l100l.U. Riboflavin 4.4 mg. Vitamin E 2.2 l.U.

are infected parenterally, in the left thoracic air sac, with 0.2 ml. of a 10' dilution of a Trypticase Soy Broth culture of Escherichia coli, the causative agent of colibacillosis in poultry. The compound 2-( 2-a'mino-5- 1,3,4-thiadiazolyl)-l-methyl-S-nitroimidazole is administered by gavage as a single oral dose in an aqueous solution of suspension, and the chicks are permitted to feed ad libitum the feed composition prepared in Example 10. Twelve days after treatment, the test is terminated and the number of survivors in each group recorded. The results are compared with two control groups of 20 chicks each, in which one control group is infected and untreated, and the second control group is uninfected and untreated. The results of the test are set forth in the following table:

*Dose is in terms of milligrams per kilogram of body weight.

Four groups of 40, 5-day old sex-lined pullet chicks are infected in the same manner as herein set forth with Escherichia coli. The compound 2-(2-acetamido-5- l ,3 ,4-thiadiazolyl)- l -methyl-5 -nitroirnidazole (Example 8) is administered by gavage as a single oral dose in an aqueous medium, and the chicks are permitted to feed ad libitum the feed composition prepared in Example 10. Twelve days after treatment, the test is terminated and the number of survivors in each group recorded. The results are compared with two control groups of 40 chicks each, in which one control group is infected and untreated, and the second control group is uninfected and untreated. The results of the test are set forth in the following table.

Three groups of 10 5-day old sex-lined pullet chick Control Infected Untreated 40 3 Uninfected Untreated 40 40 "Dose is in terms of milligrams per kilogram of body weight.

EXAMPLE 12 This example demonstrates the effectiveness of 2-( 2- amino-5-thiadiazolyl)-l-methyl-5-nitroimidazole (Example 9), and 2-(2-acetamido-5-thiadiazolyl)-lmethyl-S-nitroimidazole (Example 8) in controlling fowl typhoid.

Nine groups, eightgroups of 5 and one of 10, of oneday old sex-linked pullet chicks are infected orally by gavage with 0.5 ml. of a 10 dilution of a 5-hour Trypticase Soy Broth culture of Salmonella gallinarum, the causative agent of fowl typhoid. Each chick received approximately 6 X 10 viable cells.

Medication is administered continuously in the feed, beginning 3 hours before infection and continuing for 10 days, at which time thetest is terminated and the number of survivors in each group recorded. The results are compared with two control groups of chicks, the first group comprising 20 chicks which are infected and untreated, and the second group comprising 10 chicks which are uninfected and untreated. The results of the test are set forth in the following table.

Uninfected Untreated l Dose is in terms of percentage by weight of the feed composition prepared in Example 10.

EXAMPLE 13 Utilization of 2-(-2-Amino-5-l ,3,4-thiadiazolyl)- l thiadiazolyl)- l -methyl--nitro-imidazole in Controlling Enteritis Three groups of female Swiss Webster mice weighing 20 gm. were infected intraperitoneally with 0.5 ml. of 10 dilution of a 5-hour Trypticase Soy Broth culture of Salmonella choleraesuis var. kunzendorf, the causative agent of enteritis in pigs, an organism originally recovered from a field outbreak of Salmonella choleraesuis var. kunzendorf in pigs. Each mouse received approximately 4.6 X 10' cells as the inoculating dose.

The mice are fed a medicated feed, which is a commercial mouse chow containing the compound 2-(2 amino-5-l,3,4-thiadiadiazolyl)- l-methyl-5- nitroimidazole (Example 9), for '3 hours before infection until 7 days after infection. The mice are held for an additional 7 days after the medication is stopped, and the number of survivors in each group recorded. The medicated feed is prepared by thoroughly admixing calculated amounts of 2-(2-amino-5-l,3,4- thiadiazolyl)-l-methyl-S-nitroimidazole with commercial mouse chow to provide essentially uniform distribution in the feed offered.- The above results are compared with two control groups of ten mice each, in which one control group is infected and untreated, and the second control group is uninfected and untreated. The results of the test are set forth in the following table:

Uninfected Untreated l0 Dose is in terms of percentage by weight of the commercial mouse chow.

EXAMPLE l4 Utilization of 2-(2-Amino-5-l,3,4-thiadiazolyl)-lmethyl-S-nitro-imidazole in Controlling Trichomonas Vaginalis Infections This example demonstrates, employing two modes of administration, the efficacy of 2-(2-amino-5-l,3,4- thiadiazolyl)-l-methyl-S-nitroimidazole (Example 9) against Trichomonas vaginalis infections.

The first mode of administration, hereinafter designated Test A, employs six groups of mice, three groups of five and three groups of ten. The mice are inoculated with 50,000 culture-derived Trichomonas vaginalis (Thorns strain). The above compound is thoroughly mixed into ground feed and presented to the mice one day after inoculation. The average ad libitum drug intake, that is milligrams per kilogram of body weight per day, is estimated from the drug diet intake for 5 full days, and mouse weights taken just before and just after treatment.

The second mode of administration, hereinafter designatedTest B, employs six groups of mice, five groups of ten and one of five. The mice are inoculated with 50,000 culture-derived Trichomonas vaginalis (Thorns strain). The above compound is administered in a single oral dose by gavage 1 day after inoculation.

Six days of post inoculation scrapings, from the subcutaneous sites of inoculation, are searched microscopically for motile trichomonads, and antitrichomonal activity is concluded in those instances where motile trichomonads are eliminated from lesions present at the site of inoculation.

Mouse body weight gain from day 1 to day 6 postinoculation shows that 2-( 2-a.rnino-5-1,3,4- thiadiazolyl)-l-methyl-S-nitroimidazole is well tolerated by the animals ingesting same. Furthermore, experimentation demonstrates that more than 1,000 mg. per kilogram of body weight of said compound is well tolerated.

The results of the test are set forth in the following tables:

Dose is in terms ofmilligrams per kilogram of body weight per day.

TABLE B TABLE VI Total Compound Dose Mice Cleared Percentage Tested Cleared 2-(2-amino-5-l ,3,4- 100 mg. 56 thiadiazolyl )-l methyl-nitro- 50 mg. l0 I00 imidazole- 50 mg. l0 I0 100 25 mg. l0 9 90 12 mg. 10 7 70 6 mg. 10 2 I Dose is in terms of milligrams per kilogram of body weight.

We claim: 1. A 1,3,4:thiadiazole of the formula m N IL lN-H R-N yJ-Rr wherein R is selected from the group consisting of hydrogen and lower alkanoyl and R is selected from the group consisting of lower alkoxy and beta-(bislower alkoxy)ethyla.mino.

2. A 1,3,4-thiadiazole according to claim 1, wherein R is acetyl and R is methoxy.

3. A. 1,3,4-thiadiazole according to claim 1, wherein R is acetyl and R is B,B-diethoxyethylamino.

UNITED STATES PATENT @FFECE CERTIFICATE OT CCRRECTTCN Patent No- 3,700,684 Dated October 24, 19B

William Alan Remers, Gabriel Joseph Gibs and Inventor(s) Martin Joseph Weiss It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, in the Flowsheet, compound II, please change H NNHC" to read H NNHE'INH Column 9, Table V, please change "TABLE A" to read TEST A Also, in the Table line 18 under column headed "Cleared" add the numeral 5 Also, in the Table line 18 under column headed "Percentage Cleared" add the number lOO Column 10, Table VI, please change "TABLE B" to read TEST B Also, in the Table line 6 under the column headed "Total Mice Cleared Tested", delete "55100" and add the numeral 5 Also, in the Table, line 6, under the column headed "Percentage Cleared" add the number lOO Signed and sealed this 6th day of March 1973.

(SEAL) Attest:

ROBERT GOTTSCHALK EDWARD M.PLETCHER,JR.

Commissioner of Patents Attesting Officer USCOMM-DC 60376-5 69 U.S, GOVERNMENT PRINTING OFFICE: I969 O366-334 F ORM FO-1050 (10-69) 

2. A 1,3,4-thiadiazole according to claim 1, wherein R is acetyl and R2 is methoxy.
 3. A. 1,3,4-thiadiazole according to claim 1, wherein R is acetyl and R2 is Beta , Beta -diethoxyethylamino. 